Primary and Secondary Organic Matter Habit in Unconventional Reservoirs

Abstract Using conventional core samples from the Upper Devonian–Mississippian Bakken Formation, Williston Basin, North Dakota, U.S.A., and the Upper Cretaceous Niobrara Formation, Denver Basin, Colorado, U.S.A., as examples, the pore systems and the associated organic matter habit common in these source rocks and associated unconventional tight oil reservoirs are characterized. A workflow that distinguishes primary organic matter (kerogen) and secondary organic matter (bitumen and oil) based on their morphology, paragenesis, and general thermal history as interpreted from high-resolution scanning electron microscopy-based technologies is described in this chapter. In the description of this workflow, the quantitative image processing challenges of discriminating and quantifying pores and organic matter types are reviewed.